Method for producing liquid-crystal polyester processed product

ABSTRACT

An object is to provide a method for producing a liquid-crystal polyester processed product, the method improving the adhesion of a liquid-crystal polyester resin, which is a poorly adhesive resin. As a solution, a method for producing a liquid-crystal polyester processed product, including a step (I) of performing an oxidation treatment on a surface of a liquid-crystal polyester resin formed body including a repeating unit represented by general formula (1), is provided.

TECHNICAL FIELD

The present invention relates to a method for producing a liquid-crystalpolyester processed product, the method improving the adhesion of aliquid-crystal polyester resin, which is a poorly adhesive resin.

BACKGROUND ART

One example of a liquid-crystal polyester processed product obtainedusing a liquid-crystal polyester resin is a laminate such as a flexibleprinted circuit (FPC) including a liquid-crystal polyester formed bodyand metal foil bonded together. However, liquid-crystal polyester haslow adhesion, and sufficient adhesive strength cannot be maintained evenif an adhesive is used. Thus, the adhesive strength has been increasedtypically by physically or chemically roughening the surface of metalfoil. However, surface roughening for improved adhesion maydisadvantageously result in increased transmission loss, which isimpractical in high-speed and high-capacity transmission applications.Thus, there is a need for a liquid-crystal polyester resin having highadhesion to metal foil that is less rough, preferably, smooth.

On the other hand, various techniques of performing a surfacemodification treatment of a liquid-crystal polyester resin to increaseadhesion have also been reported. It is known that performing a coronatreatment, a plasma treatment, or the like on a liquid-crystal polyesterfilm surface improves surface wetting tension and improves adhesion tometal foil (e.g., PTL 1). NPL 1 below states that a plasma treatmentcauses polymer chain cleavage due to decomposition reaction and NorrishI reaction and causes Fries rearrangement, thereby introducing polargroups to improve adhesion, and that, alternatively, an ultravioletirradiation treatment also causes molecular chain cleavage, therebyintroducing polar groups to improve wettability and adhesion.

However, the introduction of a surface treatment step for increasingadhesion, if the treatment time is too long, induces polymer chaincleavage and thus may cause a reduction of film durability. Thus, thereis a need for an efficient method for improving the adhesion of alaminate.

In addition, liquid-crystal polyester resins are disadvantageouslydifficult to dye. Coloring by mixing such a resin with a colorant suchas a dye, a pigment, or carbon greatly reduces the strength of a resinformed body. Thus, there is also a strong need for a method forobtaining a colored liquid-crystal polyester processed product havinghigh strength.

CITATION LIST Patent Literature

-   PTL 1: Japanese Unexamined Patent Application Publication No.    03-188135

Non Patent Literature

-   NPL 1: Satoshi OKAMOTO, Journal of the Adhesion Society of Japan,    45, 290-298, (2008)

SUMMARY OF INVENTION Technical Problem

The present invention has been made in view of the circumstancesdescribed above, and an object thereof is to provide a method forproducing a liquid-crystal polyester processed product, the methodimproving the surface properties such as adhesion and colorability of aliquid-crystal polyester resin, which is a poorly adhesive resin and isdifficult to dye.

Solution to Problem

The present inventors have intensively studied in view of the problemsof the related art and found that the use of a liquid-crystal polyesterresin containing a structural unit derived from an aromatichydroxycarboxylic acid having an alkyl group on an aromatic ring such asa benzene ring allows wetting tension to be improved by a short-timesurface treatment, thereby completing the present invention.

The present invention is as follows.

1. A method for producing a liquid-crystal polyester processed product,including a step (I) of performing an oxidation treatment on a surfaceof a liquid-crystal polyester resin formed body including a repeatingunit represented by general formula (1) below.

(In formula, Ar represents a phenylene group, a naphthylene group, or abiphenylene group, R₁ represents a linear or branched alkyl group having1 to 6 carbon atoms or a cyclic alkyl group having 5 to 6 carbon atoms,and n represents an integer of 1 to 4.)

2. The method for producing a liquid-crystal polyester processed productaccording to 1, in which the oxidation treatment in the step is a plasmatreatment, a corona treatment, an ultraviolet (UV) irradiationtreatment, a flame treatment, an electron beam treatment, a chemicaltreatment with an oxidizing agent, or a heat treatment in the presenceof oxygen.

3. The method for producing a liquid-crystal polyester processed productaccording to 1 or 2, further including a step (II) of stacking a resinlayer or a metal layer on the surface on which the oxidation treatmenthas been performed to produce a laminate.

4. The method for producing a liquid-crystal polyester processed productaccording to 1 or 2, further including a step (III) of coloring thesurface on which the oxidation treatment has been performed to producecolored liquid-crystal polyester fibers.

Advantageous Effects of Invention

As compared to methods known in the art, the method for producing aliquid-crystal polyester processed product according to the presentinvention provides a liquid-crystal polyester processed product that isless likely to undergo performance degradation and has high wettingtension, and thus is very useful.

The method can improve the adhesive performance of a liquid-crystalpolyester resin, which has conventionally been a poorly adhesive resin,and thus can provide a laminate having high adhesion to smooth metalfoil.

In addition, the method can increase the binding properties of aliquid-crystal polyester resin, which has conventionally been unable tobe dyed, to dyestuff to thereby provide liquid-crystal polyesterprocessed products with a variety of hues, and thus has great advantagessuch as being applicable to textile goods.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the results of an evaluation of the wetting tension ofsurface-treated resin surfaces of Examples 1 and 2 and ComparativeExample 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail.

<Regarding Liquid-Crystal Polyester Processed Product Provided byPresent Invention>

A liquid-crystal polyester processed product related to the presentinvention means an article that has been through a step (I) ofperforming an oxidation treatment on a surface of a liquid-crystalpolyester formed body including a repeating unit represented by generalformula (1) or a product obtained by further processing the article,specifically, for example, a laminate or colored liquid-crystalpolyester fibers. One of them, the laminate will be described below.

In the laminate provided by the present invention, at least one layerincludes a layer formed of a liquid-crystal polyester resin including arepeating unit represented by general formula (1) below.

(In formula, Ar represents a phenylene group, a naphthylene group, or abiphenylene group, R₁ represents a linear or branched alkyl group having1 to 6 carbon atoms or a cyclic alkyl group having 5 to 6 carbon atoms,and n represents an integer of 1 to 4.)

In addition, a resin layer or a metal layer, or a resin layer and ametal layer are included as other layers. The laminate may be composedof two layers or more than two layers.

To obtain the laminate, the layer formed of the liquid-crystal polyesterresin including a repeating unit represented by general formula (1)above may be subjected to the below-mentioned step (I) of performing anoxidation treatment on only one surface of a formed plate or formed filmof the resin and to a step (II) of stacking a resin layer or a metallayer on the surface on which the oxidation treatment has been performedto produce the laminate, or may be subjected to the below-mentioned step(I) of performing an oxidation treatment on both surfaces of a formedplate or formed film of the resin and to the step (II) of stacking aresin layer or a metal layer on the both surfaces on which the oxidationtreatment has been performed.

Next, one of the liquid-crystal polyester processed products related tothe present invention, the colored liquid-crystal polyester fibers willbe described below.

To obtain the colored liquid-crystal polyester fibers provided by thepresent invention, the surface of a fibriform liquid-crystal polyesterformed body obtained by processing the liquid-crystal polyester resinincluding a repeating unit represented by general formula (1) above by amethod known in the art, for example, melt spinning may be colored afterthe below-mentioned step (I) of performing an oxidation treatment andsubjected to a step (III) of producing colored liquid-crystal polyesterfibers. Alternatively, the surface of a liquid-crystal polyester formedbody such as a filament yarn obtained by spinning of fibers obtained bymelt spinning, a fabric woven from fibers or yarns, or a nonwoven fabricobtained by deposition of fibers may be subjected to the step (III) ofcoloring the surface with a cationic dye or the like after thebelow-mentioned step (I) of performing an oxidation treatment.

To obtain fibers with higher strength and a higher modulus ofelasticity, the spun fibriform formed body may be heat treated in aninert gas or in vacuum, and is preferably heat treated.

Conventionally, polyester resin fibers are colored by, for example,preparation of a masterbatch with a colorant added at a stage before aspinning process, referred to as “solution dyeing”, and thus have aproblem in that the colorant added reduces fiber strength. In contrast,the fibers provided by the present invention can maintain highmechanical properties (e.g., high strength and high heat resistance)intrinsic to the liquid-crystal polyester resin because the surface offibers obtained by melt spinning or the surface of a fiber formed bodyobtained by, for example, spinning, spinning and weaving, or depositionof fibers obtained by melt spinning is colored or dyed, and thus isuseful.

<Regarding Liquid-Crystal Polyester Resin Related to Present Invention>

The liquid-crystal polyester resin including a repeating unitrepresented by general formula (1) used in the present invention isobtained by polycondensation of an aromatic hydroxycarboxylic acidand/or a derivative thereof (A) represented by general formula (1′)given below and another aromatic hydroxycarboxylic acid (B).

In general formula (1), Ar represents a phenylene group, a naphthylenegroup, or a biphenylene group. In particular, Ar is preferably aphenylene group or a naphthylene group, particularly preferably aphenylene group.

When Ar in general formula (1) is a phenylene group, the repeating unitcan be represented as general formula (2) below.

(In formula, R₁ and n are as defined in general formula (1).)

In particular, the structure represented by general formula (3) below ispreferred.

When Ar in general formula (1) is a naphthylene group, the repeatingunit can be represented as general formula (4) below.

(In formula, R₁ and n are as defined in general formula (1).)

In particular, the structure represented by general formula (5) below ispreferred.

(In formula, R₁ and n are as defined in general formula (1).)

When Ar in general formula (1) is a biphenylene group, the repeatingunit can be represented as general formula (6) below.

(In formula, R₁ is as defined in general formula (1), m and l are eachan integer of 0 to 4, and m+l is an integer of 1 to 4.)

In particular, the structure represented by general formula (7) below ispreferred.

(In formula, R₁ is as defined in general formula (1), and m and l are asdefined in general formula (6).)

R₁ in general formulae (1) to (7) above represents a linear or branchedalkyl group having 1 to 6 carbon atoms or a cyclic alkyl group having 5to 6 carbon atoms. When n, or m+l is 2 to 4, R₁ may all be the same ordifferent from each other. In particular, R₁ is preferably a linear orbranched alkyl group having 1 to 4 carbon atoms, more preferably analkyl group having one carbon atom, namely, a methyl group, or a linearor branched alkyl group having four carbon atoms, particularlypreferably a methyl group.

n in general formulae (1) to (5) above is an integer of 1 to 4. Inparticular, n is preferably 1 to 2, particularly preferably 1.

m and l in general formulae (6) and (7) above are each an integer of 0to 4, and m+l is an integer of 1 to 4. Preferably, m and l are each aninteger of 0 to 2, and m+l is 1 to 2. Particularly preferably, m and lare each an integer of 0 or 1, and m+l is 1.

<Regarding Aromatic Hydroxycarboxylic Acid and/or Derivative Thereof (A)Represented by General Formula (1′) Related to Present Invention>

The aromatic hydroxycarboxylic acid and/or derivative thereof (A)related to the present invention is a compound represented by generalformula (1′) below.

(In formula, Ar, R₁, and n are as defined in general formula (1), R₂represents a hydrogen atom or a linear or branched alkylcarbonyl grouphaving 1 to 6 carbon atoms, and R₃ represents a hydrogen atom or alinear or branched alkyl group having 1 to 6 carbon atoms.)

Preferred examples of Ar in general formula (1′) are the same as ingeneral formula (1).

When Ar in general formula (1′) is a phenylene group, the aromatichydroxycarboxylic acid and/or derivative thereof (A) can be representedas general formula (2′) below, and if this is used, a liquid-crystalpolyester resin including a repeating unit represented by generalformula (2) above will be formed.

(In formula, R₁, R₂, R₃, and n are as defined in general formula (1′).)

In particular, the structure represented by general formula (3′) belowis preferred, and if this is used, a liquid-crystal polyester resinincluding a repeating unit represented by general formula (3) above willbe formed.

(In formula, R₁, R₂, R₃, and n are as defined in general formula (1′).)

When Ar in general formula (1′) is a naphthylene group, the aromatichydroxycarboxylic acid and/or derivative thereof (A) can be representedas general formula (4′) below, and if this is used, a liquid-crystalpolyester resin including a repeating unit represented by generalformula (4) above will be formed.

(In formula, R₁, R₂, R₃, and n are as defined in general formula (1′).)

In particular, the structure represented by general formula (5′) belowis preferred, and if this is used, a liquid-crystal polyester resinincluding a repeating unit represented by general formula (5) above willbe formed.

(In formula, R₁, R₂, R₃, and n are as defined in general formula (1′).)

When Ar in general formula (1′) is a biphenylene group, the aromatichydroxycarboxylic acid and/or derivative thereof (A) can be representedas general formula (6′) below, and if this is used, a liquid-crystalpolyester resin including a repeating unit represented by generalformula (6) above will be formed.

(In formula, R₁, R₂, and R₃ are as defined in general formula (1′), mand l are each an integer of 0 to 4, and m+l is an integer of 1 to 4.)

In particular, the structure represented by general formula (7′) belowis preferred, and if this is used, a liquid-crystal polyester resinincluding a repeating unit represented by general formula (7) above willbe formed.

(In formula, R₁, R₂, and R₃ are as defined in general formula (1′), andm and l are as defined in general formula (6′).)

Preferred examples of R₁ in general formulae (1′) to (7′) above are thesame as in general formula (1).

R₂ in general formulae (1′) to (7′) above represents a hydrogen atom ora linear or branched alkylcarbonyl group having 1 to 6 carbon atoms. Inparticular, R₂ is preferably a hydrogen atom or a linear or branchedalkylcarbonyl group having 1 to 4 carbon atoms, more preferably analkylcarbonyl group having one carbon atom, namely, an acetyl group, ora linear or branched alkylcarbonyl group having four carbon atoms,particularly preferably an acetyl group.

R₃ in general formulae (1′) to (7′) above represents a hydrogen atom ora linear or branched alkyl group having 1 to 6 carbon atoms. Inparticular, R₃ is preferably a hydrogen atom or a linear or branchedalkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atomor an alkyl group having 1 to 2 carbon atoms, particularly preferably analkyl group having one carbon atom, namely, a methyl group.

Preferred examples of n in general formulae (1′) to (5′) above are thesame as in general formulae (1) to (5). Preferred examples of m and l ingeneral formulae (6′) and (7′) above are the same as in general formulae(6) and (7).

Specific examples of aromatic hydroxycarboxylic acids represented bygeneral formula (1′) include 2-methyl-4-hydroxybenzoic acid,3-methyl-4-hydroxybenzoic acid, 2,3-dimethyl-4-hydroxybenzoic acid,2,5-dimethyl-4-hydroxybenzoic acid, 2,6-dimethyl-4-hydroxybenzoic acid,3,5-dimethyl-4-hydroxybenzoic acid, 3,6-dimethyl-4-hydroxybenzoic acid,2,3,5-trimethyl-4-hydroxybenzoic acid, 2,3,6-trimethyl-4-hydroxybenzoicacid, 2,3,5,6-tetramethyl-4-hydroxybenzoic acid,2,6-dibutyl-4-hydroxybenzoic acid, 5-butyl-4-hydroxy-2-methylbenzoicacid, 5-cyclohexyl-4-hydroxy-2-methylbenzoic acid,2-methyl-3-hydroxybenzoic acid, 4-methyl-3-hydroxybenzoic acid,5-methyl-3-hydroxybenzoic acid, 6-methyl-3-hydroxybenzoic acid,2,4-dimethyl-3-hydroxybenzoic acid, 2,5-dimethyl-3-hydroxybenzoic acid,2,6-dimethyl-3-hydroxybenzoic acid, 4,5-dimethyl-3-hydroxybenzoic acid,4,6-dimethyl-3-hydroxybenzoic acid, 5,6-dimethyl-3-hydroxybenzoic acid,2,4,5-trimethyl-3-hydroxybenzoic acid, 2,4,6-trimethyl-3-hydroxybenzoicacid, 2,5,6-trimethyl-3-hydroxybenzoic acid,4,5,6-trimethyl-3-hydroxybenzoic acid,2,4,5,6-tetramethyl-3-hydroxybenzoic acid,6-hydroxy-3-methyl-2-naphthoic acid, 6-hydroxy-4-methyl-2-naphthoicacid, 6-hydroxy-5-methyl-2-naphthoic acid,6-hydroxy-7-methyl-2-naphthoic acid, 6-hydroxy-8-methyl-2-naphthoicacid, 6-hydroxy-1,3-dimethyl-2-naphthoic acid,6-hydroxy-1,4-dimethyl-2-naphthoic acid,6-hydroxy-1,5-dimethyl-2-naphthoic acid,6-hydroxy-1,7-dimethyl-2-naphthoic acid,6-hydroxy-1,8-dimethyl-2-naphthoic acid,6-hydroxy-3,4-dimethyl-2-naphthoic acid,6-hydroxy-3,5-dimethyl-2-naphthoic acid,6-hydroxy-3,7-dimethyl-2-naphthoic acid,6-hydroxy-3,8-dimethyl-2-naphthoic acid,6-hydroxy-4,5-dimethyl-2-naphthoic acid,6-hydroxy-4,7-dimethyl-2-naphthoic acid,6-hydroxy-4,8-dimethyl-2-naphthoic acid,6-hydroxy-5,7-dimethyl-2-naphthoic acid,6-hydroxy-5,8-dimethyl-2-naphthoic acid,6-hydroxy-1,3,4-trimethyl-2-naphthoic acid,6-hydroxy-1,3,5-trimethyl-2-naphthoic acid,6-hydroxy-1,3,7-trimethyl-2-naphthoic acid,6-hydroxy-1,3,8-trimethyl-2-naphthoic acid,6-hydroxy-1,4,5-trimethyl-2-naphthoic acid,6-hydroxy-1,4,7-trimethyl-2-naphthoic acid,6-hydroxy-1,4,8-trimethyl-2-naphthoic acid,6-hydroxy-1,5,7-trimethyl-2-naphthoic acid,6-hydroxy-1,5,8-trimethyl-2-naphthoic acid,6-hydroxy-1,7,8-trimethyl-2-naphthoic acid,6-hydroxy-3,4,5-trimethyl-2-naphthoic acid,6-hydroxy-3,4,7-trimethyl-2-naphthoic acid,6-hydroxy-3,4,8-trimethyl-2-naphthoic acid,6-hydroxy-3,5,7-trimethyl-2-naphthoic acid,6-hydroxy-3,5,8-trimethyl-2-naphthoic acid,6-hydroxy-3,7,8-trimethyl-2-naphthoic acid,6-hydroxy-4,5,7-trimethyl-2-naphthoic acid,6-hydroxy-4,5,8-trimethyl-2-naphthoic acid,6-hydroxy-4,7,8-trimethyl-2-naphthoic acid,6-hydroxy-5,7,8-trimethyl-2-naphthoic acid,6-hydroxy-1,3,4,5-tetramethyl-2-naphthoic acid,6-hydroxy-1,3,4,7-tetramethyl-2-naphthoic acid,6-hydroxy-1,3,4,8-tetramethyl-2-naphthoic acid,6-hydroxy-1,4,5,7-tetramethyl-2-naphthoic acid,6-hydroxy-1,4,5,8-tetramethyl-2-naphthoic acid,6-hydroxy-1,4,7,8-tetramethyl-2-naphthoic acid,6-hydroxy-1,5,7,8-tetramethyl-2-naphthoic acid,6-hydroxy-3,4,5,7-tetramethyl-2-naphthoic acid,6-hydroxy-3,4,5,8-tetramethyl-2-naphthoic acid,6-hydroxy-3,5,7,8-tetramethyl-2-naphthoic acid,6-hydroxy-4,5,7,8-tetramethyl-2-naphthoic acid,4-(2-methyl-4-hydroxyphenyl)benzoic acid,4-(3-methyl-4-hydroxyphenyl)benzoic acid,4-(5-methyl-4-hydroxyphenyl)benzoic acid,4-(6-methyl-4-hydroxyphenyl)benzoic acid,2-methyl-4-(4-hydroxyphenyl)benzoic acid,3-methyl-4-(4-hydroxyphenyl)benzoic acid,5-methyl-4-(4-hydroxyphenyl)benzoic acid, and6-methyl-4-(4-hydroxyphenyl)benzoic acid.

Specific examples of aromatic hydroxycarboxylic acid derivativesrepresented by general formula (1′) include 2-methyl-4-acetoxybenzoicacid, 3-methyl-4-acetoxybenzoic acid, 2,3-dimethyl-4-acetoxybenzoicacid, 2,5-dimethyl-4-acetoxybenzoic acid, 2,6-dimethyl-4-acetoxybenzoicacid, 3,5-dimethyl-4-acetoxybenzoic acid, 3,6-dimethyl-4-acetoxybenzoicacid, 2,3,5-trimethyl-4-acetoxybenzoic acid,2,3,6-trimethyl-4-acetoxybenzoic acid,2,3,5,6-tetramethyl-4-acetoxybenzoic acid, 2,6-dibutyl-4-acetoxybenzoicacid, 5-butyl-4-acetoxy-2-methylbenzoic acid,5-cyclohexyl-4-acetoxy-2-methylbenzoic acid, methyl2-methyl-4-hydroxybenzoate, methyl 3-methyl-4-hydroxybenzoate, methyl2,3-dimethyl-4-hydroxybenzoate, methyl 2,5-dimethyl-4-hydroxybenzoate,methyl 2,6-dimethyl-4-hydroxybenzoate, methyl3,5-dimethyl-4-hydroxybenzoate, methyl 3,6-dimethyl-4-hydroxybenzoate,methyl 2,3,5-trimethyl-4-hydroxybenzoate, methyl2,3,6-trimethyl-4-hydroxybenzoate, methyl2,3,5,6-tetramethyl-4-hydroxybenzoate, methyl2,6-dibutyl-4-hydroxybenzoate, methyl5-butyl-4-hydroxy-2-methylbenzoate, methyl5-cyclohexyl-4-hydroxy-2-methylbenzoate, ethyl2,6-dibutyl-4-hydroxybenzoate, ethyl 5-butyl-4-hydroxy-2-methylbenzoate,ethyl 5-cyclohexyl-4-hydroxy-2-methylbenzoate, ethyl2-methyl-4-hydroxybenzoate, ethyl 3-methyl-4-hydroxybenzoate, ethyl2,3-dimethyl-4-hydroxybenzoate, ethyl 2,5-dimethyl-4-hydroxybenzoate,ethyl 2,6-dimethyl-4-hydroxybenzoate, ethyl3,5-dimethyl-4-hydroxybenzoate, ethyl 3,6-dimethyl-4-hydroxybenzoate,ethyl 2,3,5-trimethyl-4-hydroxybenzoate, ethyl2,3,6-trimethyl-4-hydroxybenzoate, ethyl2,3,5,6-tetramethyl-4-hydroxybenzoate, methyl2-methyl-4-acetoxybenzoate, methyl 3-methyl-4-acetoxybenzoate, methyl2,3-dimethyl-4-acetoxybenzoate, methyl 2,5-dimethyl-4-acetoxybenzoate,methyl 2,6-dimethyl-4-acetoxybenzoate, methyl3,5-dimethyl-4-acetoxybenzoate, methyl 3,6-dimethyl-4-acetoxybenzoate,methyl 2,3,5-trimethyl-4-acetoxybenzoate, methyl2,3,6-trimethyl-4-acetoxybenzoate, methyl2,3,5,6-tetramethyl-4-acetoxybenzoate, methyl2,6-dibutyl-4-acetoxybenzoate, methyl5-butyl-4-acetoxy-2-methylbenzoate, methyl5-cyclohexyl-4-acetoxy-2-methylbenzoate, ethyl2-methyl-4-acetoxybenzoate, ethyl 3-methyl-4-acetoxybenzoate, ethyl2,3-dimethyl-4-acetoxybenzoate, ethyl 2,5-dimethyl-4-acetoxybenzoate,ethyl 2,6-dimethyl-4-acetoxybenzoate, ethyl3,5-dimethyl-4-acetoxybenzoate, ethyl 3,6-dimethyl-4-acetoxybenzoate,ethyl 2,3,5-trimethyl-4-acetoxybenzoate, ethyl2,3,6-trimethyl-4-acetoxybenzoate, ethyl2,3,5,6-tetramethyl-4-acetoxybenzoate, ethyl2,6-dibutyl-4-acetoxybenzoate, ethyl 5-butyl-4-acetoxy-2-methylbenzoate,ethyl 5-cyclohexyl-4-acetoxy-2-methylbenzoate,6-acetoxy-3-methyl-2-naphthoic acid, 6-acetoxy-4-methyl-2-naphthoicacid, 6-acetoxy-5-methyl-2-naphthoic acid,6-acetoxy-7-methyl-2-naphthoic acid, 6-acetoxy-8-methyl-2-naphthoicacid, methyl 6-hydroxy-3-methyl-2-naphthoate, methyl6-hydroxy-4-methyl-2-naphthoate, methyl 6-hydroxy-5-methyl-2-naphthoate,methyl 6-hydroxy-7-methyl-2-naphthoate, methyl6-hydroxy-8-methyl-2-naphthoate, ethyl 6-hydroxy-3-methyl-2-naphthoate,ethyl 6-hydroxy-4-methyl-2-naphthoate, ethyl6-hydroxy-5-methyl-2-naphthoate, ethyl 6-hydroxy-7-methyl-2-naphthoate,ethyl 6-hydroxy-8-methyl-2-naphthoate, methyl6-acetoxy-3-methyl-2-naphthoate, methyl 6-acetoxy-4-methyl-2-naphthoate,methyl 6-acetoxy-5-methyl-2-naphthoate, methyl6-acetoxy-7-methyl-2-naphthoate, methyl 6-acetoxy-8-methyl-2-naphthoate,ethyl 6-acetoxy-3-methyl-2-naphthoate, ethyl6-acetoxy-4-methyl-2-naphthoate, ethyl 6-acetoxy-5-methyl-2-naphthoate,ethyl 6-acetoxy-7-methyl-2-naphthoate, ethyl6-acetoxy-8-methyl-2-naphthoate,2-methyl-4-hydroxy-4′-biphenylcarboxylic acid,3-methyl-4-hydroxy-4′-biphenylcarboxylic acid,2,5-dimethyl-4-hydroxy-4′-biphenylcarboxylic acid,2,5-dibutyl-4-hydroxy-4′-biphenylcarboxylic acid,2,2′-dimethyl-4-hydroxy-4′-biphenylcarboxylic acid,2-methyl-4-acetoxy-4′-biphenylcarboxylic acid,3-methyl-4-acetoxy-4′-biphenylcarboxylic acid,2,5-dimethyl-4-acetoxy-4′-biphenylcarboxylic acid,2,5-dibutyl-4-acetoxy-4′-biphenylcarboxylic acid,2,2′-dimethyl-4-acetoxy-4′-biphenylcarboxylic acid,2-methyl-4-hydroxy-4′-biphenylcarboxylic acid methyl ester,3-methyl-4-hydroxy-4′-biphenylcarboxylic acid methyl ester,2,5-dimethyl-4-hydroxy-4′-biphenylcarboxylic acid methyl ester,2,5-dibutyl-4-hydroxy-4′-biphenylcarboxylic acid methyl ester,2,2′-dimethyl-4-hydroxy-4′-biphenylcarboxylic acid methyl ester,4-(2-methyl-4-acetoxyphenyl)benzoic acid,4-(3-methyl-4-acetoxyphenyl)benzoic acid,4-(5-methyl-4-acetoxyphenyl)benzoic acid,4-(6-methyl-4-acetoxyphenyl)benzoic acid,2-methyl-4-(4-acetoxyphenyl)benzoic acid,3-methyl-4-(4-acetoxyphenyl)benzoic acid,5-methyl-4-(4-acetoxyphenyl)benzoic acid,6-methyl-4-(4-acetoxyphenyl)benzoic acid, methyl4-(2-methyl-4-hydroxyphenyl)benzoate, methyl4-(3-methyl-4-hydroxyphenyl)benzoate, methyl4-(5-methyl-4-hydroxyphenyl)benzoate, methyl4-(6-methyl-4-hydroxyphenyl)benzoate, methyl2-methyl-4-(4-hydroxyphenyl)benzoate, methyl3-methyl-4-(4-hydroxyphenyl)benzoate, methyl5-methyl-4-(4-hydroxyphenyl)benzoate, methyl6-methyl-4-(4-hydroxyphenyl)benzoate, ethyl4-(2-methyl-4-hydroxyphenyl)benzoate, ethyl4-(3-methyl-4-hydroxyphenyl)benzoate, ethyl4-(5-methyl-4-hydroxyphenyl)benzoate, ethyl4-(6-methyl-4-hydroxyphenyl)benzoate, ethyl2-methyl-4-(4-hydroxyphenyl)benzoate, ethyl3-methyl-4-(4-hydroxyphenyl)benzoate, ethyl5-methyl-4-(4-hydroxyphenyl)benzoate, ethyl6-methyl-4-(4-hydroxyphenyl)benzoate, methyl4-(2-methyl-4-acetoxyphenyl)benzoate, methyl4-(3-methyl-4-acetoxyphenyl)benzoate, methyl4-(5-methyl-4-acetoxyphenyl)benzoate, methyl4-(6-methyl-4-acetoxyphenyl)benzoate, methyl2-methyl-4-(4-acetoxyphenyl)benzoate, methyl3-methyl-4-(4-acetoxyphenyl)benzoate, methyl5-methyl-4-(4-acetoxyphenyl)benzoate, methyl6-methyl-4-(4-acetoxyphenyl)benzoate, ethyl4-(2-methyl-4-acetoxyphenyl)benzoate, ethyl4-(3-methyl-4-acetoxyphenyl)benzoate, ethyl4-(5-methyl-4-acetoxyphenyl)benzoate, ethyl4-(6-methyl-4-acetoxyphenyl)benzoate, ethyl2-methyl-4-(4-acetoxyphenyl)benzoate, ethyl3-methyl-4-(4-acetoxyphenyl)benzoate, ethyl5-methyl-4-(4-acetoxyphenyl)benzoate, and ethyl6-methyl-4-(4-acetoxyphenyl)benzoate.

<Regarding Other Aromatic Hydroxycarboxylic Acid (B)>

Specific examples of compounds that can be used as the other aromatichydroxycarboxylic acid (B) include p-hydroxybenzoic acid,m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and4-hydroxy-4′-biphenylcarboxylic acid.

<Regarding Other Polycondensation Components>

In polycondensing the aromatic hydroxycarboxylic acid and/or derivativethereof (A) represented by general formula (1′) with the other aromatichydroxycarboxylic acid (B) to obtain the liquid-crystal polyester resinaccording to the production method of the present invention, componentssuch as a dihydroxy compound (C), a dicarboxylic acid compound (D), analiphatic diol (E), and an aliphatic dicarboxylic acid (F) can befurther used in combination.

Specific examples of compounds that can be used as the compound (C) thatcan be used as a dihydroxy compound include hydroquinone, resorcinol,2,6-naphthalenediol, 1,5-naphthalenediol, 4,4′-dihydroxybiphenyl,4,4′-dihydroxy-3,3′-dimethylbiphenyl,4,4′-dihydroxy-3,3′,5,5′-tetramethylbiphenyl,4,4′-dihydroxy-2,2′,3,3′,5,5′-hexamethylbiphenyl,2,2′-bis(4-hydroxyphenyl)isopropyl, 2,7-dihydroxyanthraquinone,bis(4-hydroxyphenyl)sulfone, 4,4′-dihydroxybenzophenone, and carboxylicacid ester derivatives thereof.

Specific examples of compounds that can be used as the dicarboxylic acidcompound (D) include terephthalic acid, isophthalic acid,2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,4,4′-biphenyldicarboxylic acid, 4,4′-dicarboxydiphenyl ether,4,4′-dicarboxydiphenyl sulfide, 1,2-bis(4-carboxyphenoxy) ethylene, andester derivatives thereof.

As a compound that can be used as the aliphatic diol (E), specifically,an aliphatic diol represented by general formula (8) below can be used.

[Chem. 16]

R₂O—R₄—OR₂  (8)

(In formula, R₄ represents an alkylene group having 2 to 12 carbonatoms, and R₂ is as defined in general formula (1′).)

Specific examples include ethylene glycol, propylene glycol, andcarboxylic acid ester derivatives thereof.

As a compound that can be used as the aliphatic dicarboxylic acid (F),specifically, an aliphatic dicarboxylic acid represented by generalformula (9) below can be used.

[Chem. 17]

R₃OOC—R₅—COOR₃  (9)

(In formula, R₅ represents an alkylene group having 2 to 12 carbonatoms, and R₃ is as defined in general formula (1′).)

Specific examples include malonic acid, succinic acid, glutaric acid,adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, andester derivatives thereof.

In the liquid-crystal polyester resin including a repeating unitrepresented by general formula (1), the content of the component (A),relative to the total content of the component (A) and the otheraromatic hydroxycarboxylic acid (B), is in the range from a lower limitof 1 mol % or more, preferably 3 mol % or more, more preferably 5 mol %or more, still more preferably 7 mol % or more to an upper limit of 50mol % or less, preferably 45 mol % or less, more preferably 40 mol % orless, still more preferably 35 mol % or less. If the content of thecomponent (A) is less than 1 mol %, the effect of improving surfacewetting tension obtained by performing an oxidation treatment on asurface of a liquid-crystal polyester resin formed body will beinsufficient, which is undesirable. If the content of the component (A)is more than 50 mol %, the physical properties of the liquid-crystalpolyester, such as heat resistance and mechanical strength, will bedegraded, which is undesirable.

In the liquid-crystal polyester resin including a repeating unitrepresented by general formula (1), when the component (A) and thecomponent (B), and, furthermore, the component (C), the component (D),the component (E), and the component (F) are used in combination, thecontent of the component (A), relative to the total content of thecomponents (A) to (F), is in the range from a lower limit of 1 mol % ormore, preferably 3 mol % or more, more preferably 5 mol % or more, stillmore preferably 7 mol % or more to an upper limit of 50 mol % or less,preferably 45 mol % or less, more preferably 40 mol % or less, stillmore preferably 35 mol % or less. Also in this case, if the content ofthe component (A) is less than 1 mol %, the effect obtained byperforming an oxidation treatment on a surface of a liquid-crystalpolyester resin formed body will be insufficient. If the content of thecomponent (A) is more than 50 mol %, the physical properties of theliquid-crystal polyester resin, such as heat resistance and mechanicalstrength, will be degraded, which is undesirable.

<Regarding Method for Producing Liquid-Crystal Polyester Resin>

The method for producing the liquid-crystal polyester resin including arepeating unit represented by general formula (1) related to the presentinvention is not particularly limited. The liquid-crystal polyesterresin can be produced in accordance with a known polycondensation methodfor a liquid-crystal polyester resin. Industrially, the liquid-crystalpolyester resin can be produced, for example, by a polycondensationreaction using a transesterification method.

For example, when the liquid-crystal polyester resin is produced fromthe aromatic hydroxycarboxylic acid and/or derivative thereof (A)represented by general formula (1′) and the other aromatichydroxycarboxylic acid (B), the liquid-crystal polyester resin may beproduced by, for example, acylating a phenolic hydroxyl group using afatty acid anhydride and then performing a de-fatty acidpolycondensation reaction. When it is desired to increase the molecularweight of the liquid-crystal polyester resin for a higher melting pointand higher mechanical strength, solid phase polymerization may beperformed in an inert gas atmosphere under reduced pressure.

The reaction temperature in the above acylation is preferably in therange of 100° C. to 160° C., more preferably 140° C. or higher. If thisreaction temperature is excessively low, the acylation may proceedinsufficiently to leave behind the monomers in a polymerization product,which is undesirable.

The above de-fatty acid polycondensation reaction is preferablyperformed in the range of 100° C. to 350° C., more preferably in therange of 150° C. to 310° C. If this reaction temperature is low, thepolymerization will not proceed sufficiently, which is undesirable. Thereaction pressure may be normal pressure or reduced pressure, and ispreferably reduced pressure (about 10.0 kPa) in order to distillvolatiles (e.g., acetic acid, water, and alcohols) formed as by-productsout of the reaction system.

Although the polycondensation reaction of the liquid-crystal polyesterresin proceeds in the absence of catalyst, an acetic acid metal salt,titanium alkoxide, magnesium oxide, or the like can be used.

The melting point of the liquid-crystal polyester resin including arepeating unit represented by general formula (1) related to the presentinvention is preferably 200° C. or higher, more preferably 210° C. orhigher, still more preferably 220° C. or higher. The melting point ofthe liquid-crystal polyester resin can be determined by, for example,differential scanning calorimetry.

<Regarding Liquid-Crystal Polyester Resin Formed Body>

The method for obtaining the liquid-crystal polyester resin formed bodyhaving a repeating unit represented by general formula (1) related tothe present invention is not particularly limited, and a known methodcan be used.

When a laminate is produced, a liquid-crystal polyester formed bodyhaving a block shape, a plate shape, a sheet shape, a film shape, orother shape can be obtained by, for example, forming a liquid-crystalpolyester in a molten state after completion of the polycondensationreaction by extrusion molding or injection molding, forming aliquid-crystal polyester resin dissolved in a solvent by solutioncasting, or press forming a powdered liquid-crystal polyester resin.

When fibers are produced, they can be obtained by, for example,pulverizing a liquid-crystal polyester resin in a molten state aftercompletion of the polycondensation reaction as it is or after beingformed into a plate shape, a sheet shape, or other shape, melting theresulting powdery product, and performing melt spinning. To obtainfibers with higher strength and a higher modulus of elasticity, the spunfibers may be heat treated in an inert gas or in vacuum, and ispreferably heat treated.

The liquid-crystal polyester formed body can also be obtained in theform of, for example, a filament yarn obtained by spinning of fibersobtained by melt spinning, a fabric woven from fibers or yarns, anonwoven fabric obtained by deposition of fibers.

The liquid-crystal polyester resin formed body related to the presentinvention may be a formed body composed only of the liquid-crystalpolyester resin including a repeating unit represented by generalformula (1) or a formed body composed of an alloy of the liquid-crystalpolyester resin as the principal component and other thermoplasticresins. Examples of other thermoplastic resins that can be used includepolypropylene, polyethylene, polybutylene terephthalate, nylon 6, nylon66, polyphenylene sulfide, polycarbonate, polyphenylene ether, andliquid-crystal polyester resins other than the liquid-crystal polyesterresin related to the present invention.

<Regarding Step (I) of Performing Oxidation Treatment>

The production method of the present invention includes a step (I) ofperforming an oxidation treatment on a surface of the liquid-crystalpolyester resin formed body. The oxidation treatment in the step (I) ofthe present invention may be performed by any method that can producethe advantageous effects of the present invention, and a known methodcan be used. For example, a plasma treatment, a corona treatment, anultraviolet (UV) irradiation treatment, a flame treatment, an electronbeam treatment, a chemical treatment with an oxidizing agent, or a heattreatment in the presence of oxygen may be used.

In the plasma treatment, a gas introduced into an apparatus is convertedinto the plasma state in the ambient atmosphere or under reducedpressure by barrier discharge using a dielectric disposed on a surfaceof an electrode such as a parallel plate electrode or a coaxial cylinderelectrode or by application of a high-frequency wave or a microwave, andthe resulting plasma is applied to the formed body, whereby theoxidation treatment of the formed body surface can be performed. Theplasma treatment performed under atmospheric pressure does not requiretime for decompression or any large-scale equipment such as a vacuumchamber and is suitable for continuous treatment, and thus is preferredas an oxidation treatment in the present invention.

In the corona treatment, the formed body is disposed between aninsulated electrode and a counter electrode, a high-frequency highvoltage is applied to generate corona discharge, and a gas componentexcited or dissociated by the corona discharge is applied to the formedbody, whereby the oxidation treatment of the formed body surface can beperformed.

In the ultraviolet (UV) irradiation treatment, the formed body surfaceis irradiated with ultraviolet radiation using an ultraviolet irradiatorthat can emit short-wavelength ultraviolet radiation (e.g., wavelength:about 100 to 290 nm), whereby the oxidation treatment of the formed bodysurface can be performed. The ultraviolet irradiator may be, forexample, a low-pressure mercury lamp, a KrCl excimer lamp, or a Xe₂excimer lamp.

In the flame treatment, gas molecules are converted into plasma with theheat and temperature of a flame, and the oxidation treatment of theformed body surface can be performed by the same action as in the plasmatreatment.

The electron beam treatment is performed by irradiating the formed bodysurface with an electron beam generated using an electron linearaccelerator. The atmosphere for the electron beam irradiation treatmentmay be the ambient atmosphere or an atmosphere in which theconcentration of oxygen is adjusted with, for example, an inert gas(e.g., nitrogen). The electron beam irradiation may be performed using ahigh-energy type electron beam irradiator that emits an electron beam atan energy of 100 keV to 400 keV or a low-energy type electron beamirradiator that emits an electron beam at an energy of 100 keV or less,and an irradiator of any irradiation type such as scanning type orcurtain type may be used. For example, a curtain type electronirradiator (LB1023 manufactured by EYE ELECTRON BEAM CO., LTD.) or aline-irradiation type low-energy electron beam irradiator (EB-ENGINE(registered trademark) manufactured by Hamamatsu Photonics K.K.) can beused.

In the chemical treatment with an oxidizing agent, a chemical solutioncontaining an oxidizing agent is brought into contact with the formedbody surface, whereby the oxidation treatment of the formed body surfacecan be performed. Examples of oxidizing agents that can be used includepermanganates such as potassium permanganate and sodium permanganate andchromic acids such as chromic acid mixtures of potassium dichromate andsulfuric acid.

In the heat treatment in the presence of oxygen, heat is applied to theliquid-crystal polyester formed body in an oxygen-containing atmosphere,for example, the ambient atmosphere, whereby the oxidation treatment ofthe formed body surface can be performed.

By performing an oxidation treatment on the surface of the formed bodyobtained using the liquid-crystal polyester resin related to the presentinvention, as compared to when conventional liquid-crystal polyestersare used, good surface wettability can be provided even if the oxidationtreatment time in the step (I) is short, thus enabling efficientproduction of a laminate and improvement in colorability of theliquid-crystal polyester resin difficult to dye. Thus, the presentinvention is useful.

Here, the improvement in wettability of the liquid-crystal polyesterresin formed body surface is probably due to the following reason: inthe liquid-crystal polyester resin having a repeating unit representedby general formula (1) according to the present invention, the alkylgroup (R₁) bonded to Ar in general formula (1) is converted to anoxidized polar group by the oxidation treatment in the step (I).

<Regarding Step (II) of Stacking Resin Layer or Metal Layer on Surfaceon which Oxidation Treatment has been Performed to Produce Laminate>

The production method of the present invention may further include,after the oxidation treatment in the step (I), a step (II) of stacking aresin layer or a metal layer on the surface on which the oxidationtreatment has been performed to produce a laminate.

Specific examples of the resin layer stacked in the step (II) includeresin layers formed of saturated polyester resins, polysulfone resins,polytetrafluoroethylene resins, polyimide resins, polyester imide,polyetherimide resins, polyamide-imide resins, polyamide resins,polyphenylene ether resins, polyethersulfone resins, polyether ketoneresins, polythioether ketone resins, polyether ether ketone resins,thermoplastic polyurethane resins, polyolefin resins, ABS resins,polyamide elastomers, polyester elastomers, epoxy resins, novolacresins, benzoxazin resins, BT resins, and silicone resins. These resinsfor use can be used also when they are resin compositions containingdesired additives and fillers.

The method of stacking the resin layer in the step (II) is notparticularly limited, and a known method can be used. For example, onthe formed body surface treated in the step (I) of performing anoxidation treatment on a surface of the liquid-crystal polyester resinformed body in the present invention, the resin layer may be formed by acasting method, thermocompression bonding of a film resin, orapplication of an uncured liquid thermosetting resin and heat curingthereof.

Specific examples of the metal layer stacked in the step (II) includecopper, gold, silver, nickel, and aluminum, among which copper issuitable.

The method of stacking the metal layer in step (II) is not particularlylimited, and a known method can be used. For example, on the formed bodysurface treated in the step (I) of performing an oxidation treatment onthe liquid-crystal polyester resin formed body surface related to thepresent invention, the metal layer may be stacked by thermocompressionbonding of metal foil, vapor deposition, electroless plating, orelectrolytic plating.

Alternatively, the metal layer may be stacked on an adhesive resin layerstacked on the surface of the liquid-crystal polyester formed body, butthe metal layer is preferably stacked on the surface of theliquid-crystal polyester formed body without forming an adhesive resinlayer.

<Regarding Step (III) of Coloring Surface on which Oxidation Treatmenthas been Performed to Produce Colored Liquid-Crystal Polyester Fibers>

The production method of the present invention may include a step (III)of coloring the surface on which the oxidation treatment has beenperformed to produce colored liquid-crystal polyester fibers. Inparticular, coloration using a pigment having a cationic group canprovide binding to the modified surface of the liquid-crystal polyesterresin formed body after the oxidation treatment, thus providing acolored liquid-crystal polyester processed product.

The pigment having a cationic group can be selected from known pigmentcompounds having at least one cationic group. Examples include C.I.Basic Red 1 (rhodamine 6GCP), 8 (rhodamine G), C.I. Basic Violet 10(rhodamine B), C.I. Basic Violet 11, C.I. Basic Blue 1 (Basic Cyanine6G), Basic Blue 5 (Basic Cyanine EX), Basic Blue 7 (Victoria Pure BlueBO), Basic Blue 25 (Basic Blue GO), Basic Blue 26 (Victoria BlueBconc.), C.I. Basic Green 1 (Brilliant Green GX), Basic Green 4(malachite green), C.I. Basic Violet 1 (methyl violet), C.I. BasicViolet 3 (crystal violet), C.I. Basic Violet 14 (Magenta), Lauth'sViolet, methylene blue, methylene green B, C.I. Basic Blue 9, C.I. BasicBlue 17, C.I. Basic Blue 24, C.I. Basic Yellow 1, C.I. Basic Violet 44,C.I. Basic Violet 46, C.I. Basic Blue 116, C.I. Basic Yellow 11, 12, 13,14, 21, 22, 23, 24, 28, 29, 33, 35, 40, 43, 44, 45, 48, 49, 51, 52, 53,C.I. Basic Red 12, 13, 14, 15, 27, 35, 36, 37, 45, 48, 49, 52, 53, 66,68, C.I. Basic Violet 7, 15, 16, 20, 21, 39, 40, C.I. Basic Orange 27,42, 44, 46, and C.I. Basic Blue 62, 63.

EXAMPLES

The present invention will now be described more specifically withreference to Examples, but it should be noted that the present inventionis not limited to these Examples.

The melting point and the wetting tension were measured by the followingmethods.

[Method of Analysis] 1. Measurement of Melting Point (DifferentialScanning Calorimetry: DSC)

About 10 mg of a crystal was weighed into an aluminum pan, and using adifferential scanning calorimeter (DSC-60 manufactured by ShimadzuCorporation), the measurement was performed under the followingoperating conditions using aluminum oxide as a control.

(Operating Conditions)

Heating rate: 20° C./min

Measurement temperature range: 40° C. to 320° C.

Measurement atmosphere: nitrogen, 50 mL/min

2. Measurement of Wetting Tension

The wetting tension of a surface-treated resin surface was measuredaccording to JIS K 6768. A wetting tension test mixture (manufactured byFUJIFILM Wako Pure Chemical Corporation) was used as a test solution.The test solution was applied to a test piece with a cotton swab, andthe wettability of the surface was visually observed to measure thewetting tension. The test was performed multiple times to ensurereproducibility.

Example 1

A reaction vessel equipped with a stirring blade and a distillation pipewas charged with 65.6 g of p-hydroxybenzoic acid, 72.3 g of4-hydroxy-2-methylbenzoic acid, 65.9 g of 6-hydroxy-2-naphthoic acid,and 135.5 g of acetic anhydride, and an acetylation reaction was carriedout at 150° C. for 3 hours. The temperature was then increased to 310°C. over 4 hours. At 310° C., the pressure was reduced to 10 kPa over 15minutes, and polymerization was carried out for 1 hour. As a result, aliquid-crystal polyester resin having a melting point of 246° C. (bydifferential scanning calorimetry) was obtained. The reaction formula isshown below.

(In formula, x, y, and z are 0.270, 0.365, and 0.365, respectively.)

The liquid-crystal polyester resin obtained by synthesis was pulverized,and using a pressing machine (TOYOSEIKI MINI TEST PRESS, model: MP-2FH),a SUS304 stainless steel mold for resin pressing, and a polyimide film(manufactured by Ube Industries, Ltd.), a uniformly smoothliquid-crystal polyester resin sheet having a thickness of 1 mm wasfabricated. The resin sheet was cut to a predetermined size to prepare atest piece.

The test piece prepared was irradiated with atmospheric pressure plasmagenerated by dielectric barrier discharge for a certain period of timeusing a plasma treatment tester (manufactured by Alpha Co., Ltd., model:PTM-100-9kVS-V2, frequency: 20 kHz, output voltage: 9 kV, ratedcapacity: 80 W, treatment distance: 2.5 mm), thereby being surfacetreated.

The wetting tension of the surface-treated resin surface was thenmeasured according to JIS K 6768. A wetting tension test mixture(manufactured by FUJIFILM Wako Pure Chemical Corporation) was used as atest solution. The test solution was applied to the test piece with acotton swab, and the wettability of the surface was visually observed tomeasure the wetting tension.

Example 2

Synthesis of a liquid-crystal polyester resin was performed in the samemanner as in Example 1 except that 117.4 g of p-hydroxybenzoic acid,14.5 g of 4-hydroxy-2-methylbenzoic acid, 65.9 g of6-hydroxy-2-naphthoic acid, and 135.7 g of acetic anhydride were used,to obtain a liquid-crystal polyester resin having a melting point of256° C. (by differential scanning calorimetry). The same forming,treatment, and evaluation as in Example 1 were then performed.

(In formula, x, y, and z are 0.270, 0.656, and 0.074, respectively.)

Comparative Example 1

Synthesis of a liquid-crystal polyester resin was performed in the samemanner as in Example 1 except that 131.1 g of p-hydroxybenzoic acid,66.1 g of 6-hydroxy-2-naphthoic acid, and 135.4 g of acetic anhydridewere used and 4-hydroxy-2-methylbenzoic acid was not used, to obtain aliquid-crystal polyester resin having a melting point of 279° C. (bydifferential scanning calorimetry). The same forming, treatment, andevaluation as in Example 1 were then performed. The reaction formula isshown below.

(In formula, x and y are 0.270 and 0.730, respectively.)

The results of the evaluation of the wetting tension of thesurface-treated resin surfaces of Examples 1 and 2 and ComparativeExample 1 are shown in Table 1 and FIG. 1 below.

TABLE 1 Plasma treatment Surface wetting time (s) tension (mN/m) Example1 untreated 44 0.2 59 0.5 59 Example 2 untreated 44 0.2 58 0.5 59Comparative Example 1 untreated 37 0.2 46 0.5 44 2   54

The results in Table 1 show that in Examples 1 and 2, in which theoxidation treatment was performed on a surface of the liquid-crystalpolyester resin formed body including a repeating unit represented bygeneral formula (1) of the present invention, the surface wettingtension was dramatically improved with a treatment performed for soshort a time as 0.2 seconds.

In contrast, in Comparative Example 1, in which the oxidation treatmentwas performed on a surface of a conventional liquid-crystal polyesterresin formed body derived from p-hydroxybenzoic acid having no alkylgroups, the surface wetting tension was lower than those in Examples 1and 2 even when the treatment time was 2 seconds.

When the time of the oxidation treatment on a liquid-crystal polyesterresin formed body surface is long, the molecular chain of theliquid-crystal polyester resin is damaged to weaken the formed body, andthus long-term reliability is lost, and a preferred liquid-crystalpolyester processed product cannot be obtained. Probably, if the surfaceis modified to have improved adhesion in the short term, the surface ofthe weakened material is easily deteriorated by, for example, heating orcooling during use, and the adhesion and colorability cannot bemaintained.

The above results show that by using the liquid-crystal polyester resinformed body including a repeating unit represented by general formula(1) of the present invention, the surface wetting tension isdramatically improved in a shorter time than in conventional cases, and,for example, when a laminate is formed as a liquid-crystal polyesterprocessed product, the adhesion to a metal layer having conductivity canbe further increased.

The liquid-crystal polyester resin formed bodies of Examples 1 and 2have a surface wetting tension of 44 mN/m before surface treatment,which is higher than the surface wetting tension of Comparative Example1 before surface treatment, 37 mN/m. Although the reason for this is notclear, it is presumed that the alkyl group represented by R₁ in generalformula (1) is oxidized by heating during forming of the liquid-crystalpolyester resin and converted into a polar group such as a carboxylgroup, thereby improving the surface wetting tension.

1. A method for producing a liquid-crystal polyester processed product,comprising a step (I) of performing an oxidation treatment on a surfaceof a liquid-crystal polyester resin formed body including a repeatingunit represented by general formula (1):

wherein Ar represents a phenylene group, a naphthylene group, or abiphenylene group, R₁ represents a linear or branched alkyl group having1 to 6 carbon atoms or a cyclic alkyl group having 5 to 6 carbon atoms,and n represents an integer of 1 to
 4. 2. The method for producing aliquid-crystal polyester processed product according to claim 1, whereinthe oxidation treatment in the step is a plasma treatment, a coronatreatment, an ultraviolet (UV) irradiation treatment, a flame treatment,an electron beam treatment, a chemical treatment with an oxidizingagent, or a heat treatment in the presence of oxygen.
 3. The method forproducing a liquid-crystal polyester processed product according toclaim 1, further comprising a step (II) of stacking a resin layer or ametal layer on the surface on which the oxidation treatment has beenperformed to produce a laminate.
 4. The method for producing aliquid-crystal polyester processed product according to claim 1, furthercomprising a step (III) of coloring the surface on which the oxidationtreatment has been performed to produce colored liquid-crystal polyesterfibers.
 5. The method for producing a liquid-crystal polyester processedproduct according to claim 2, further comprising a step (II) of stackinga resin layer or a metal layer on the surface on which the oxidationtreatment has been performed to produce a laminate.
 6. The method forproducing a liquid-crystal polyester processed product according toclaim 2, further comprising a step (III) of coloring the surface onwhich the oxidation treatment has been performed to produce coloredliquid-crystal polyester fibers.